High-energy radiation monitoring based on radio-fluorogenic co-polymerization II: fixed fluorescent images of collimated x-ray beams using an RFCP gel

Abstract

We have produced an optically clear, close to water-equivalent gel that is radio-fluorogenic, i.e. fluoresces in UV light after exposure to high-energy radiation. Its potential as a 2D and 3D dosimetric medium is demonstrated by fixed fluorescent images of the cross-section, track and intersection of collimated (10 × 10 or 5 × 5 mm(2)) 205 kVp x-ray beams. The images, produced by doses on the order of 10 Gy, are formed instantaneously and can be digitally recorded and scanned with a spatial resolution on the order of 0.1 mm. No loss of spatial resolution occurs on standing under ambient conditions for at least 3 days.

A Radio‐Fluorogenic Organic Gel for Real‐Time, 3D Radiation Dosimetry

“…The dependence is seen to be close to linear, even at the maximum, illustrating the large dynamic range of the present method. The slight supra‐linear dependence indicated has been found in previous measurements 3. The dose and dose rate dependencies are being more thoroughly investigated by homogeneous irradiation procedures using cobalt‐60 sources.…”

“…We have previously shown how radio‐fluorogenic co‐polymerization (RFCP) can be used to monitor the radiation dose in a small volume of a liquid radio‐fluorogenic solution 1, 2. More recently we have devised a method of preparing a quasi‐rigid RFCP gel that has been shown to be capable of creating a fixed fluorescent image of an X‐ray beam 3. The radio‐fluorogenic property of the gel is based on the conversion of non‐fluorescent maleimido‐pyrene into the fluorescent succinimido‐ derivative on co‐polymerization into radiation‐initiated growing chains of a bulk acrylic monomer (illustrated in the table‐of‐contents figure).…”

“…The gel consists of partially (ca 15%) pre‐polymerized tertiary‐butyl acrylate (tBuA) containing ca 100 ppm maleimido‐pyrene (MPy). The gel preparation procedure has been fully described elsewhere 3. A 2 cm square glass cell containing a 6 cm length of such a gel is shown in Figure A.…”

A radio-fluorogenic polymer-gel makes fixed fluorescent images of complex radiation fields

“…The problem at the time was to find a suitable bulk medium capable of immobilizing the fluorescent radiolytic product but still allowing polymerization to take place. The breakthrough came serendipitously in 2008 when we discovered that TBA itself formed a quasi-rigid gel when irradiated to a monomer conversion of ~15%, corresponding to a γ-ray dose of approximately 10 Gy [12,13].…”

“…Over the 10x10x35 mm 3 volume of the gel the dose rate within the GC200 cavity varied by less than 2% [24]. Rather than a linear or sub-linear dependence on dose, the results actually display a super-linear dose dependence of the fluorescence intensity [12,21,25]. This is also found for the dose dependence of monomer conversion in pure TBA [13] and is attributed to a decrease in the rate of radical-radical recombination as the viscosity of the medium increases.…”